An atomic absorption spectrophotometer is provided with an atomizing unit for heating and atomizing a sample. At the atomizing unit, a sample is atomized, thereby generating atomic vapor, and measurement light is radiated in the atomic vapor by a light source. At this time, light of a specific wavelength is absorbed in the atomic vapor, and thus, analysis of the sample may be performed by measuring the absorbance (for example, see Patent Documents 1 and 2).
The measurement light which has passed through the atomic vapor is detected by a detector. The detector may be configured from a photomultiplier tube, for example. An output signal from the detector is amplified by an amplifier, and is then input to a control unit via an A/D converter. At the control unit, the absorbance is measured based on the ratio between the received intensity of measurement light when light is absorbed in the atomic vapor and the received intensity of measurement light when light is not absorbed.
With a general atomic absorption spectrophotometer, light that reaches the detector includes, in addition to the measurement light from the light source as described above, light from outside the device, light occurring at the atomizing unit and the like, for example. As the light occurring at the atomizing unit, light emission from the structure of the atomizing unit accompanying heating, light emission from the sample itself and the like may be cited. Among these light emissions, light emission from the sample itself has a property that the amount of light emission is greater as the concentration of the sample is higher.
With this type of atomic absorption spectrophotometer, depending on the measurement conditions, the amount of light emission from the structure of the atomizing unit accompanying heating may change, and a signal voltage of the detector (detector signal voltage) may exceed the maximum voltage that can be measured. Accordingly, Patent Document 1 proposes a configuration for storing detector signal voltages for all the settable combinations of wavelengths, slit widths, and atomizing temperatures of the atomizing unit. Then, at the time of sample measurement, an amplifier is controlled by an optimum detector signal amplification factor based on the detector signal voltage stored in relation to the wavelength, the slit width, and the atomizing temperature used for the sample measurement.
However, even with the configuration in Patent Document 1, depending on the measurement conditions (wavelength, slit width, flame species, gas flow rate), the detector signal voltage may exceed the maximum voltage that can be measured and accurate measurement is sometimes prevented. Thus, Patent Document 2 proposes a configuration for storing an optimal value of the detector signal voltage for an A/D converter corresponding to a combination of measurement conditions that may be simultaneously set. Then, when measurement conditions are set, a voltage adjustment section or a signal amplifier is adjusted so that the optimal value of a corresponding detector signal voltage is input to the A/D converter.